The formation of various types of cards such as IC cards has been proposed by utilizing a very thin semiconductor device. Hitherto, it has been difficult to obtain such cards which can stand use in practical applications owing to the ease in breakage by bending stress.
Conventional assembling technologies of thin semiconductor devices are described, for example, in "LSI Handbook" (edited by the Electronic Communication Society and published by Ohom Corporation on Nov. 30, 1984, pp. 406-416). In these conventional semiconductor device assembling technologies, there have been employed semiconductor wafers which have such a thickness of approximately 200 .mu.m or over that they are very unlikely to break when direct handling is done.
As is well known in the art, a polishing method has been in wide use for thinning a semiconductor wafer. In order to uniformly process a semiconductor wafer, for example, with a process accuracy of 5% according to the polishing method, it is essential that the semiconductor wafer be set parallel to a polishing device at high accuracy and high reproducibility. For realizing such a very high level of parallel setting, a very expensive apparatus is necessary, thus having involved a difficulty in practical applications.
An attempt has been made to effect a polishing method while monitoring the thickness of a semiconductor wafer. If a region with a large area is polished according to this method, it takes a very long time, resulting in the lowering of productivity.
Alternatively, when a semiconductor wafer is polished to a very small thickness, for example, of approximately 0.1 .mu.m there arises the problem that various types of semiconductor devices, such as transistors, formed on the surface of the semiconductor wafer are broken owing to the stress caused by the polishing.
Moreover, when such a thinned semiconductor chip is directly handled according to the prior art technologies, a problem is involved in that the semiconductor chip is broken. Thus, it has been difficult to form a semiconductor device in high yield at low costs.